The present invention relates to syringe assemblies and particularly to syringe assemblies having an automatic disabling mechanism.
Throughout the world the multiple use of hypodermic syringe products which are intended for single-use only, is instrumental in drug abuse and in the transfer of contagious diseases. Intravenous drug users who routinely share and re-use syringes are a high-risk group with respect to the AIDS virus. Also, the effects of multiple use are a major concern in some countries where repeated use of syringe products during mass immunization programs may be responsible for the spread of many diseases. Re-use of single-use hypodermic syringe assemblies is also instrumental in the spread of drug abuse even in the absence of infection or disease.
Many attempts have been made to remedy this problem. Most notable are early contributions which relies on a specific act to destroy the syringe after use either by using a destructive device or providing syringe assembly with frangible zones so that the syringe could be rendered inoperable by the application of force. Other attempts involve the inclusion of structure which would allow the destruction or defeating of the syringe function by a conscious act of the syringe user. Although many of these devices work quite well, they require the specific intent of the user followed by the actual act to destroy or render the syringe inoperable. These devices are not effective with a user having the specific intent to re-use the hypodermic syringe. Accordingly, there was a need for a single-use hypodermic syringe which after use will become inoperable or incapable of further use automatically without any additional act on the part of the user. The automatic function is much harder to provide because the means for rendering the syringe inoperable must not prevent its filling or use under normal conditions.
Single-use syringes which automatically disable after injection are taught in the art. Some of these syringes contain a locking element positioned in the syringe barrel between the plunger rod and the inside surface of the barrel. In use, the syringe allows the user to draw a pre-selected amount of medication into the chamber of the barrel and deliver this medication, as through injection, into the patient. Any attempt to withdraw the plunger to use the syringe a second time will cause the locking element to embed itself into the inside surface of the barrel to prevent proximal motion of the plunger rod.
Many times a traditional multi-use syringe and needle assembly are used to reconstitute lyophilized medication. The steps for reconstitution include withdrawing sterile water from a stoppered vial or glass ampoule into the syringe barrel and then delivering this water into a stoppered vial or glass ampoule containing the lyophilized medication. The reconstituted medication is then drawn into a single-use syringe for delivery to the patient. Single-use syringes designed specifically for reconstitution and which cannot be used for injecting medication into a patient are not presently available.
Further, mass immunization programs usually take place in developing countries where resources are limited. Accordingly, sometimes with limited resources a number of people immunized can be increased if the cost of the medication and/or the syringe is reduced. It is not desirable to reduce the cost of the single-use syringe by compromising its features since those intent on re-using syringes can be very aggressive and resourceful in their attempts to disable the safety features.
Accordingly, there is always a needle for single-use syringes which are more cost-effective and more resistant to improper re-use. Further, there is a need for a single-use syringe which is only capable of reconstitution of a dried or lyophilized drug substances and not capable of injection into the human body.